The purpose of this study was to evaluate the in vivo migration patterns of a polished femoral component cemented line-to-line using EBRA –FCA. The series included 164 primary consecutive THAs performed in 155 patients with a mean age of 63.8 years. A single prosthesis was used combining an all-polyethylene socket and a 22.2 mm femoral head. The monoblock double tapered femoral component made of 316-L stainless steel had a highly polished surface (Ra 0.04 micron) and a quadrangular section (Kerboull(r) MKIII, Stryker). The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem prior to the line-to-line cementation. Stem subsidence was evaluated using EBRA-FCA software which accuracy is better than ± 1.5 mm (95% percentile), with a specificity of 100% and a sensitivity of 78% for detection of migration of more than 1.0 mm, using RSA as the gold standard.Introduction
Methods
We have evaluated the in vivo migration patterns of 164 primary consecutive Charnley-Kerboull total hip replacements which were undertaken in 155 patients. The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem before line-to-line cementing. We used the Ein Bild Roentgen Analyse femoral component method to assess the subsidence of the femoral component. At a mean of 17.3 years (15.1 to 18.3) 73 patients were still alive and had not been revised, eight had been revised, 66 had died and eight had been lost to follow-up. The mean subsidence of the entire series was 0.63 mm (0.0 to 1.94). When using a 1.5 mm threshold, only four stems were considered to have subsided. Our study showed that, in most cases, a highly polished double-tapered stem cemented line-to-line does not subside at least up to 18 years after implantation.
We describe 129 consecutive revision total hip replacements using a Charnley-Kerboull femoral component of standard length with impaction allografting. The mean follow-up was 8.2 years (2 to 16). Additionally, extramedullary reinforcement was performed using struts of cortical allograft in 49 hips and cerclage wires in 30. There was one intra-operative fracture of the femur but none later. Two femoral components subsided by 5 mm and 8 mm respectively, and were considered to be radiological failures. No further revision of a femoral component was required. The rate of survival of the femoral component at nine years, using radiological failure as the endpoint, was 98%. Our study showed that impaction grafting in association with a Charnley-Kerboull femoral component has a low rate of subsidence. Reconstruction of deficiencies of distal bone with struts of cortical allograft appeared to be an efficient way of preventing postoperative femoral fracture for up to 16 years.
Controversy exists with regard to the thickness of cement mantles that are necessary around the femoral components of cemented total hip arthroplasties. Conventional teaching, based on bench-top or computor models and theoretical analyses, as well as post-mortem &
follow-up studies, suggests that the cement mantle should be complete and not less than 2–3mm in thickness. Mantles that are less than this are held to be at risk from mechanical failure in the long term; if they are incomplete, focal lysis may occur and progress to aseptic loosening. However, long term experience with a number of French cemented femoral components suggests that these conventions may be erroneous. These French femoral components include the Charnley-Kerboull (stainless steel) and the Ceraver Osteal (Ti6Al4V) stems, in both of which the underlying design principle is that the stem should completely fill the femoral canal, the cement then being used purely to fill the gaps. Such a design philosophy implies that the cement mantles will be very thin, and since both of these stems are straight and the femoral medullary canal is not, the mantles may not only be thin, but also in places incomplete. Conventional teaching would suggest that any stem utilising mantles of this type would fail from a combination of focal lysis and cement fracture. Yet the long term results of both of these stems have been outstandingly good, with extremely low levels of aseptic loosening and endosteal lysis, irrespective of the bearing combinations being used. Both these stems have a surface finish of Ra <
0.1 microns. A third French design, the Fare stem, manufactured from Ti6Al4V and based on the same principles, was associated with bad results when manufactured with a rough (>
1.5 microns) surface, and appreciably better results after the surface roughness was changed to <
0.1 microns. These findings, that constitute the ‘French Paradox’, have profound implications for the mechanical behaviour of cement in the femur and for the mechanisms that underlie stem failure from loosening.
Eighty-nine patients (8 males, 81 females) with an average age of 52 years had 119 high dislocations (Crowe IV, 30 bilateral and 59 unilateral). The patients underwent 118 total hip arthroplasties between 1970 and 1986 using original or modified Charnley prostheses. Only 39 patients had not had a previous operation. Pain in the hip associated with stiffness and limitation in activity was the main indication for surgery. Back or knee pain was the chief complaint of 11 patients. Pre-operatively and post-operatively, a thorough assessment of the patients was made including hips, pelvis lumbosacral spine, knee, leg length discrepancy and static body balance. The operation was performed through a transtrochanteric approach. A small socket was always inserted and cemented into the true acetabulum augmented by an autogenous graft, and a straight femoral component implanted at the level of the lesser trochanter. Muscle releases and tenotomies were not performed. Twenty-nine patients (35 hips) had died or were lost to follow-up. Sixty patients were still alive at the last examination in 1996, and regularly seen with a mean follow-up of 16 years. The mean follow-up of the whole series was 12.8 years. At the last examination, clinical results according to the d’Aubigne rating system were classified as excellent 59.3%, very good 15.2%, good 15.2%, fair 5.1%, and poor 5%. Only 10 patients had a persistent waddling gait and a positive Trendelenburg sign. The results were slightly less good when a major femoral angulation needed an alignment osteotomy. One femoral and seven acetabular loosenings were revised. In addition, five hips were revised for severe polyethylene wear and osteolysis before definite loosening, and two hips for heterotopic ossifications. The rate of revision was 12.7%. At twenty years, the survival rate was 99% for the femoral component and 87% for the socket, cemented fixation as end point, whereas the cumulative survival rate of the prosthesis was 78%, revision as end point. The leg shortening, mean 4.84 cm (range 3-8 cm), was accurately corrected 63 times and within 1 cm 42 times. The lengthening was an average of 3.80 cm (2 to 7 cm). Leg length discrepancy was, on the whole, reduced as much as possible (mean 2.6 cm pre-operatively, 0.4 cm post-operatively). Of the 18 pre-operative painful knees, 10 were greatly improved, but four of these needed an operation. Lateral pelvic tilt was corrected in more than 50%, pelvic frontal asymmetry was substantially reduced, as well as lordosis and lateral curve of the lumbar spine. As a result, low back pain has been relieved in 40 patients, but two required a laminectomy for a lumbar canal stenosis. Total hip arthroplasty on high riding hips may be a wonderful operation, but this operation is full of pitfalls, technically demanding, and may represent a serious risk of complication. A successful result depends on a complete pre-operative assessment of the patient, a perfectly performed surgical procedure, and a reasonable selection of its indications.